Clean Magento cache by cache tag instead of only the config cache.

[Vinai]

The context MageTest\MagentoExtension\Context\MagentoContext provides the step definition for I clear the cache.
This in fact only clears the Magento configuration cache.
It would be useful to be able to do I clear the "block_html" cache or I clear the complete cache

The class MageTest\MagentoExtension\Service\CacheManager already provides the method addSection().

Reference:

MageTest\MagentoExtension\Context\MagentoContext::theCacheIsClean()
MageTest\MagentoExtension\Service\CacheManager::clear()
MageTest\MagentoExtension\Service\CacheManager::addSection()
MageTest\MagentoExtension\Service\Cache\ConfigurationCache::clear()